The invention concerns a device for the measuring and adjustment of the motion of mechanical structural members in hydraulic systems operating with electroviscous fluids (EVF). Such a device consists in principle of a flow channel filled with the electroviscous fluid and provided with electrodes, or of a closed system with electrodes which are moved with respect to each other, whereby in both cases there is electric voltage on the electrodes. These devices are shown in FIGS. 7 and 8 of GB 12 82 568. Structural members of this kind are used in electrically controlled active vibration absorbers, shock absorbers, mountings or couplings.
Electroviscous fluids (EVF) are dispersions of finely-distributed hydrophilic solids in hydrophobic oils which are not electrically conductive. Under the influence of an adequately strong electric field the viscosity of the EVF can be changed very quickly and reversibly from the fluid to the plastic or solid state. In order for the EVF to be excited, both constant electric fields and alternating fields can be used. The electricity outputs required for this are relatively low.
The application possibilities of the EVF in hydraulic systems are known in principle, for example in hydraulic valves without moving parts and in hydraulic cylinders (for example, U.S. Pat. No. 2,661,596) , in vibration generators (for example U.S. Pat. No. 3,984,086), viscosity couplings (for example U.S. Pat. Nos. 2,417,850 and 2,661,825, DE-OS 3.128.959), shock absorbers (for example, U.S. Pat. No. 3,207,269) or twin-chamber engine bearings with hydraulic damping (EP-OS 0.137.112).
All these hydraulic systems are characterised in that they have at least two stationary or mobile electrode surfaces, structured as desired, between which the EVF is situated. By the application of variable electric voltage the speed of the flow of the fluid, for example, and thus the falling pressure of the EVF between the stationary electrodes or the frictional connection between mobile electrode surfaces can be controlled within broad ranges. For this purpose high-voltage industrial equipment, for example, with a constant or variable output voltage, can be used.
In a large number of cases of practical application, the automatic adjustment of the hydraulic system with a dependency on the conditions of motion at that time should be achieved. For example, in the case of a shock absorber or a vibration absorber, the viscosity of the EVF should always be set with the aid of the control voltage in such a way that a desired level of damping is attained for all loads. For this purpose a regulator circuit is necessary which can be sensitive to the condition of motion of the hydraulic system at the time with the aid of appropriate sensors (for example, transducers, speed sensors or acceleration sensors), and which produces the voltage necessary for optimal viscosity control using an algorithm.
Because of the need to build-in motion sensors of this type including the measuring cable and measuring instruments associated with them, the overall construction of the hydraulic system becomes more expensive, more complicated and, possibly, more susceptible to failure, in particular if the installation must take place in locations which are not easily accessible.
This is where the invention comes into its own. The basis was the object of finding a simple method of controlling and adjusting the hydraulic EVF system without the necessity of also incorporating motion sensors. It makes it possible for a simple, compact construction of the entire hydraulic system to be achieved.